定直线

directrix of a parabola

to set / to fix / to determine / to decide / to order

surname Zhi / Zhi (c. 2000 BC), fifth of the legendary Flame Emperors 炎帝[Yan2 di4] descended from Shennong 神農|神农[Shen2 nong2] Farmer God

straight / to straighten / fair and reasonable / frank / straightforward / (indicates continuing motion or action) / vertical / vertical downward stroke in Chinese characters

straight line / sharply (rise or fall)

variant of 線|线[xian4]

thread / string / wire / line / CL:條|条[tiao2],股[gu3],根[gen1] / (after a number) tier (unofficial ranking of a Chinese city)